Hi all, I am new to Six Sigma and currently, despite a lot of reading and googling, I am unable to figure out the relation between CTQ and Opportunity for defects. Some books state that a single CTQ is a single opportunity for defects, some says that for 1 CTQ there might be more opportunities for defects. What is the relation then?

An example of contradiction:

This site has an example: CTQ Name: Board Functionality, with 58 opportunites to defects.

Book Six Sigma for dummies state that “Number of CTQ equals to number of defect opportunities.

In simplest terms a CTQ is a specific measurement of a customer’s expectation. I.E Call back within 4 minutes, Delivery within 4 hours etc. It is an output measure of the process.

Defect definition is not meeting customer expectations of your product or service. This is also an output measure.

To answer your question they are closely related but also very different. One is a measure of expectation, the other a measure of failure to meet expectation(s).

You can have single or multiple ways to fail to meet your CTQ defined as defect opportunities.

Think of a personal check you write to someone else. Your Customer’s CTQ may be to get money from the writer (you) into their bank account. Basically pass/fail.

There are multiple defect opportunities in that personal check that may prevent a successful transaction. Failure to write an amount, failure to sign, missing or illegible bank and/or routing numbers, cash in your account to cover the payment.

To meet your CTQ you do have multiple defect opportunities that could prevent success, making your check defective.

I think you are trying to tie them too closely together. As John stated, a CTQ is more about the voice of the customer rather than a defect opportunity. It is a way to translate the VOC to an internal metric. I tell my class it represents your internal language. If you VOC says they want a reliable product, the CTQ might be time to failure. The time to failure can then be measured with metrics. The CTQ is more specific to your company’s understanding. There could be a hundred reasons for the product to fail with would be defect opportunities.